Investigating the role of the D0 domain of KIR3DL1 in ligand interaction and exploring the effect of LILRB1 on KIR3DL1 signaling

• Author / Creator

  Fu, Li

• Natural killer (NK) cells are crucial in early defense against viral infections by rapidly terminating infected cells and by secreting cytokines to shape adaptive immune responses. The activity of NK cells is regulated by balance of activating and inhibitory signals during interaction with target cells. Inhibitory receptors are important as they trigger inhibitory signals to prevent damage of normal health tissue through interaction with self MHC-I molecules. KIR3DL1 is one of inhibitory receptors implicated in resistance to viral diseases such as HIV/AIDS. Structurally, KIR3DL1 contains three Ig domains and has specificity for MHC-I molecules belonging to the HLA-Bw4 serogroup. The receptor’s second (D1) and third (D2) Ig domains confer the Bw4 specificity, but the role of the first Ig domain (D0) in ligand recognition remained enigmatic until recently.
  In this thesis, I found that KIR3DL1 expressed in YTS cells and as a soluble receptor can weakly recognize additional MHC-I molecules including HLA-B*0702 and HLA-G. This interaction is highly sensitive to blocking with antibodies to the MHC-I a3-domain and the anti-KIR3DL1-D0 antibody, Z27, but not the canonical blocking antibody DX9. Using chimeric receptors between KIR3DL1 and KIR2DL1 expressed on YTS cells and as soluble Fc-fusion proteins, I showed that the presence of a second and independent site of interaction between the KIR3DL1-D0 domain and MHC-I proteins. This data is consistent with the finding of the D0 domain interaction with the MHC-I α1 region in the co-crystal structure reported by Vivian JP et al in 2012. However, after reconciling antibody blocking results with the published co-crystal structure, I proposed a new model in which a third site of interaction occurs. Moreover, using same strategies, I showed KIR3DL1 binding to xenogenic MHC-I, such as mouse MHC-I. Similarly as shown in HLA, either anti-α3 antibodies or Z27 dramatically inhibited the binding. In addition, mutagenesis studies showed that position 194 at the α3 domain somehow interferes KIR3DL1 binding with unknown mechanism.
  
  Collectively, the results may shed light on how KIRs evolved, and be used to interpret genetic association of KIR with diseases such as HIV/AIDS.

• Subjects / Keywords

  • KIR3DL1
  • Ligand interaction

• Graduation date

  Fall 2013

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3X63BG8Q

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.